Carton



June 26, 1962 A. w. HAGAN 3,040,958

CARTON Filed Oct. '7, 1957 4 Sheets-Sheet 2 INVENTOR ALBERT W. HAGAN ATTORNEYS June 26, 1962 A. w. HAGAN 3,040,958

CARTON Filed Oct. '7, 1957 4 Sheets-Sheet 3 ",2 7 T i l'l I'l Z i 121M" HM Y HM W INVENTOR A 455K7- W. HAGHN ATTORNEYS I June 26, 1962 A. w. HAGAN 3,040,958

CARTON Filed Oct. '7, 1957 4 Sheets-Sheet 4 INVENTOR B ALBERT WHAGAN BY a #fd/bF/U ATTORNEYS United States Patent Office 3,040,958 Patented June 26, 1962 3,040,958 CARTON Albert W. Hagan, Stratford, Conn., assignor to Roy S. Sanford & Company, Oxford, Conn., a partnership Filed Oct. 7, 1957, Ser. No. 688,576 2 Claims. (Cl. 229-37) This invention relates to cartons of paper-board, fiberboard and sheet materials suitable for the formation of cartons having foldable end flaps, and particularly to a novel sift-proof construction for a carton of the above type. The terms paper-board and fiberboard are used interchangeably in the specification and claims.

One of the objects of the present invention is to provide a novel paper-board carton blank which is readily adapted for quick and eificient sealing, the construction being such that complete sea-ling of all pin holes and cracks is achieved, thus providing a container having end portions which are completely sift-proof when the carton is utilized for powdered materials such as flour, for example.

Another object of the invention is the provision of a carton construction so constituted as to eliminate the need for inner bags or overwraps commonly utilized for the purpose of preventing sifting of the powdered contents.

A further object of the invention is to provide a siftproof carton of polygonal cross section formed from a single piece of low cost material such as paper-board.

Still another object of the invention is to provide a one-piece carton blank scored to permit folding in such a manner as to permit efficient and positive sealing of the end flaps under relatively low pressure.

A still further object of the invention is to provide a sift-proof carton of paper-board or the like, so constructed as to effectively seal the corners against leakage of the contents without relying on adhesive to seal the pin holes whichcornmonly are found in cartons of this general type.

In the manufacture of paper-board cartons of this general type, it is not too diflicult to properly seal one end of the container, since when the first end is sealed, the end flaps can be held together under high pressure, a mandrel being inserted in the container to support the flaps on one side, and a pressure plate being placed against the flaps on the outside in order to properly seal the flaps. Difiiculty is experienced, however, in sealing the other end of the container after it has been filled, and it is a further and important object of the invention to overcome this ditficulty, and to provide a construction wherein the end of the carton which is sealed after filling of the carton can be made sift-proof with very little pressure being applied to the folded end flaps which close the end of the carton.

A still further object of the invention is to provide a new and novel corner construction for a carton.

Yet another object of the invention is to provide a corner construction for a paper-board carton which will stand rough handling without causing the corners of the carton to leak.

Other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when taken in connection with the accompanying drawings, wherein several embodiments of the invention are illustrated. It is to be expressly understood, however, that the drawings are utilized for purposes of illustration only, and are not to be taken as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings, wherein similar reference characters refer to similar parts throughout the several views;

FIG. 1 is a view of a blank adapted to be formed into a carton of the above type;

FIG. 2 is a view of a modified form of carton blank;

FIG. 3 is a fragmentary view of another modified form of carton blank;

FIG. 4 is a fragmentary view of a further modification of the carton blank; i

FIG. 5 is a view of still another modified form of carton blank;

FIG. 6 is a perspective view showing one step in the formation of one corner of a carton from the blank shown in FIG. 1;

FIG. 7 is a perspective view showing another step in the formation of the corner of the carton of FIG. 6;

FIG. 8 is a perspective view of a further step in the formation of the carton corner of FIG. 6;

FIG. 9 shows a step in the formation of one corner of a carton from the blank of FIG. 5;

FIG. 10 shows another step in the formation of the corner of FIG. 9; Y

FIG. 1:1 shows another step in the formation of the corner of FIG. 9;

FIG. 12 is a perspective view of a portion of a completed carton formed from the blank shown in FIG. 1;

FIG. 13 is a perspective view of a portion of a com.- pleted carton formed from the blank shown in FIG. 2;

FIG. 14 is a perspective view of a portion of a completed carton formed from the blank shown in FIG. 3 and FIG. 15 is a perspective view of a mandrel and pressure pad for forming the end of a carton.

The present invention is particularly directed to a carton construction which is economical in the use of paperboard, which can be readily fabricated, and which does not require complicated folding mechanism in order to produce a sift-proof carton. In this connection, it should be noted that the corner of a conventional carton of the type utilized for the packaging of flour, cake mixes or the like, is a very rigid structure, and that in the event the carton is dropped on the floor and hits on a corner of the carton, the carton is generally damaged at the corners to such an extent as to cause serious sifting of the contents. In the event an overwrap is used, this is generally ruptured at the corner, and since the carton itself is not sift-proof at the corner, leakage occurs. It is well known that such cartons receive rather rough handling in chain grocery stores and the like, and consequently the loss due to damaged cartons is quite high.

The carton of the present invention has a corner construction which overcomes these difficulties, since the corner is not rigid in the sense that the corners of a conventional carton are rigid, and while crushing of the corner due to dropping the cartons may change the appearance of the corner by crushing some of the paperboard, it does not cause leakage or sifting at the corners. Cartons of this construction have been dropped repeatedly from heights of two or three feet without causing sifting of the contents, the contents utilized in these tests being very finely ground flour. Explaining the matter in another way, it is pointed out that the rigid corner of the conventional carton buckles when dropped on the floor, thus rupturing the paper-board, while the carton of the present invention may be considered to have the corners already buckled slightly, so that further displacement can occur without rupturing the paper-board.

Referring more particularly to FIG. 1, the present invention is illustrated therein as including a container blank 4, shown for convenience in a vertical position, having main wall panels 5, 6, 7, and 8, and a glue flap panel 9 adapted to be adhesively secured to the edge portion of the wall panel 5, the inner surface of the blank being shown. The Wall panels and 6 are con nected by a fiat narrow vertical panel 10, wall panels 6 and 7 are connected by a flat narrow vertical panel 11, wall panels 7 and 8 are connected by a flat narrow vertical panel 12, and the wall panel 8 is connected to the glue flap 9 by means of a flat narrow vertical panel 13. The edges of these narrow panels are defined as shown by separate spaced apart vertical score lines 1 4, said flat narrow vertical corner panels, as shown in the drawings, being unscored between said spaced apart vertical score lines. The narrow vertical panels 10, 11, 12 and 13 are very narrow relative to the width of the main sidewall panels, and consequently, when the carton is folded into a tubular shape with the glue flap 9* connected to the panel 5, the resulting carton tube is essentially rectangular in cross section, and there is a fiat narrow vertical panel at each corner of the carton tube having a surface preferably disposed at an angle of 135 to the panels on either side thereof. 1

7 Since both ends of the carton blank in this figure are shown as substantially identical, only the upper end will be referred to in detail in the description immediately following. A score line or fold line 15 extends across the carton at the upper end at substantially right angles to the vertical score lines 14, and foldable end flaps 16, 17, 18 and 19 are connected respectively to sidewall panels 5, 6, 7 and 8 along this score line. In addition a small end flap or extended glue "flap 20 may be utilized connected with the glue fla 9 and a portion of the narrow vertical panel 13 along the score line 15. The end flaps 16, 17, 18 and 19 are separated from each other as by means of cut lines 21, 22 and 23, the flap 19 being separated from the small flap 20 by a similar cut line 24. The term cut lines refers to the separation of the end flaps, either by single cut lines or by the removal of paper-board between the flaps. It will be noted that the above referred to cut lines are preferably substantially in alignment with the vertical center lines of the panels 10, 11, 12 and 13 respectively, and that they are preferably but not necessarily terminated slightly above the horizontal score line 15. Adhesive coatings 25 of any suitable type are applied to the large end flaps 17 and 19 as shown, and although the adhesive is shown as covering the entire inner surfaces of these flaps, it will be understood, as will be more fully explained hereinafter, that other adhesive patterns may be utilized without departing from the principles of the invention. In addition, a narrow strip of adhesive is applied along the edge of the vertical wall panel 5 in order to secure this panel to the outer surface of the glue flap 9. In like manner, a narrow strip of adhesive 28 is applied to the left edge of the 'end flap 16 in order to secure the latter to the outside surface of the panel 20 when the blank is folded into tubular form.

At the bottom end of the carton blank, the construction is, as heretofore stated, the same as that at the upper end of the blank, and includes end flaps 29, 30, 31, 32 and 33 all arranged in the same manner as the end flaps at the upper end of the blank, these lower end flaps being separated as by means of cut lines 34, 35, 36 and 37, also arranged in the same manner as the cut lines 21, 22, 23 and 24 at the other end of the blank. These end flaps also include adhesive coatings 38, 39 and 40, arranged in a manner corresponding to the adhesive coatings 28, 25 and 26 at the upper end of the blank.

In setting up the carton, the blank is preferably folded around a mandrel 41, shown in elementary form in FIG. 15 of the drawings, this mandrel having flat relieved corner portions 42 adapted to conform to the narrow vertical panels on the blank when the latter is folded, and a fiat top portion 43 against which the end flaps are folded to close the end of the carton. A pressure block 44 is provided, and when the end flaps on the first end to be closed have been folded with the adhesive coatings therebetween, the pressure block is moved downward by suitable means, not shown, in order to press the flaps together. During this closing operation, the blank is first wrapped around the mandrel, and the left side of the panel 5 is brought into overlapping relationship with the glue flap 9 on the outer surface thereof, the end flap 16 likewise being brought into overlapping relationship with the outer surface of the panel 20. At the other end of the blank, the left side of the end fla 29 is brought into overlapping relationship with the outer surface of the small end panel 33. The overlapping portions are adhesively secured together, the result being a tube which assumes the cross-sectional shape of the finished carton. Thereupon, the upper end panels 16 and 18 are folded downward at right angles to the adjacent wall panels 5 and 7 against the upper end 43 of the mandrel, and thereafter, the panels 19 and 17 are folded inward in the order named over the outer surfaces of the panels 16 and 18, being secured thereto and to each other by the adhesive coatings 25 and 26. The pressure pad 44 is now moved downward in order to press the flaps together in sealing relationship. As will be more fully explained hereinafter, when the panels are folded as above described, small nibs of paper-board are left protruding outwardly at the corners, and these nibs, the arrangement of which will be more fully described hereinafter, serve to effectively seal the corners and prevent any sifting of powdered material from the carton. It is pointed out again, in this connection, that very little pressure is required to form the end of the carton, the pressure pad 44 acting against the folded end flaps merely serving to insure uniform contact therebetween.

Following the above operations, the carton is inverted, the lower end now becoming the top of the carton. The carton is then filled with the desired material, whereupon the end flaps 29 and 31 are folded inwardly at right angles to their adjacent wall panels, following which panels 32 and 30 are folded inwardly in overlapping relationship in the order named, although it is to be understood that the order of folding of these flaps as well as the flaps 17 and 19 at the other end of the container can be reversed if desired, and it is to be further noted that if desired, the large end flaps can be folded first in overlapping relationship, and the small end flaps can be folded over thereafter. The construction described is the preferred construction, however, since it results in a better appearance and an unbroken surface on the end of the carton.

The folding of the end flaps at one corner of the carton is shown in enlarged perspective views of FIGS. 6, 7 and 8. It will be noted that when the blank is folded in tubular form with the end flaps still unfolded, the lower ends of the cut lines between the end flaps join the apex of a more or less triangular portion 45 of the carton material, the bottom of the triangular portion being defined by the horizontal score line 15. If desired, as shown in FIG. 4, the other two sides of this triangular portion may be defined by score lines 46 and 46a. These score lines are not necessary in all cases, but in some types of paper-board, they assist in the proper folding of the end flaps when the end is being closed. In FIG. 6, the corner of the carton is shown before any of the end flaps have been folded and the triangular portion 45 can be readily seen. As the next step in the end closing operation, see FIG. 7, one of the end flaps may be folded downward at right angles to the adjacent wall panel, and it will be seen that the triangular portion 45 tends to fold along the sides of the triangle tending partially to fill the corner of the container. In the next step, the other flap may be folded inwardly on top of the first flap, the end flaps forming an outstanding nib 46b, see FIG. 8. Since the inner surface of one panel is coated with adhesive, it adheres firmly to the other panel. It will be apparent from the foregoing that the nib is in the form of what might be termed a bellows fold, and that the paper is crowded together in this fold in such a manner as to effectively seal the corner regardless of whether or not the adhesive extends fully into the corner, the same action occurring at the other corners.

Assuming that the flaps just folded are on the last end of the box to be closed, it will be apparent that the lower portion of the carton with its closed bottom forms a fairly rigid member when subjected to vertical compression loads, and that a light force exerted on the top of the canton against the folded end flaps is suflicient to form a flat end on the carton. This may be done by placing a weight on the folded end flaps or by means of a suitable machine, not shown, and it is only necessary to apply sufiicient pressure to engage the end flaps with each other and to flatten the nibs 46b downward substantially into the plane of the remaining portion of the top end of the canton. It has been found that very little pressure is required to accomplish this. From the foregoing, it will be noted that in the event a pin hole is formed at the corner it must be positioned at the apex of the outstanding nib, and since the construction is such that paperboard at the location of this pin hole is crowded very lightly together due to the nature of the fold and due to the arrangement of the narrow corner panels 12, the pin hole is completely sealed and will not be subsequently opened up in such a Way as to leak even though it may be crushed by dropping the carton on a hard surface. It should also be noted, referring to FIGS. 1-5, that the end flap 16 is cut away on an angle at point 460 in such a manner that the angular edge portion thus formed conforms, when the blank is folded into tubular form, with one edge of the adjacent triangular portion 45, so that when the left edge of the panel 16 is adhesively joined to the outer surface of the panel 20, the panels 16 and 20 form one small end flap which can be folded in without interference. Thus, the glue flap presents no difiiculty in the forming of the corner adjacent thereto.

Due to the arrangement of the flat panels 11, 12 and 13 in the carton construction just described, the completed carton, instead of being very rigid, is quite flexible, and when handled, acts more like a bag than like a rigid carton. In the case of cartons utilized for flour and similar products, this is sometimes desired by the manufacturer, since when the end of the carton is opened to dispense the flour, the sides of the carton can be readily squeezed together to assist in properly controlling the dispensing of the flour from the carton.

In other cases, however, a more rigid type of carton is desired, and this is readily accomplished by a construction such as that shown in the blank of FIG. '2. This carton also includes main Wall panels 5, 6, and 7 and 8, and glue flap 9 as Well as upper end flaps 16, 17, 18 and 19 and extended glue flap 20, in the same manner as shown in FIG. 1. Also, the panels 16 and 17, 17 and 18, 18 and 19, and 19 and 20 are separated by cut lines 21, 22, 23 and 24, these lines terminating a short distance above the horizontal score line 15 which defines the boundary between the side wall panels and the end flaps. The construction of this carton is the same at both ends, and consequently only the upper half will be described in detail. The upper end portions of the wall panels 5, 6, 7, 8 and the glue flap 9 are connected adjacent their upper ends by fiat narrow vertical panels 4-7, 48, 49 and 50. These are located relative to the adjacent wall panels in substantially the same manner as the flat narrow vertical panels shown in FIG. 1, and the cut lines between the upper end flaps are substantially in line with the center lines of these narrow panels. The lower ends of the panels are preferably defined by diagonal score lines or fold lines 51 and 52, and these score lines merge into single score lines 53 dividing the adjacent wall panels and being substantially in alignment with the vertical center lines of panels 47, 48, 49 and 50. The same construction may be utilized at the lower end of the blank, the lower end being provided with end ffaps 29, 3G, 31, 32 and extended glue flap 33, separated respectively by cut lines 3d, 35, 36 and 37 terminating a short distance below the horizontal score line 33a. The lower end portions of the panels 5, 6, 7, 8 and 9 are connected by flat narrow vertical panels 54, 55, 56, and 57, the upper end of these panels being defined by score lines 53 and 59 which merge at their upper ends with the lower ends of the score lines 53.

When the main side panels are folded at right angles to each other to form a carton tube of substantially rectangular cross section, they told about the vertical score lines 53, and the side wall panels adjacent the score line 15 are connected by the flat narrow panels 47, 48, 49 and 50 in the same manne that the side wall panels in FIG. 1 are connected throughout their length by the narrow vertical panels 10, 11, 12 and 113. Thus, the corner construction of this carton is identical with that of the carton shown in FIG. 1, but in view of the fact that the carton sidewall panels fold about the vertical score lines 53, the central portion of the carton between the upper and lower ends of the score lines is rigid in the same manner as a conventional carton, and this rigidity is enhanced by the formation between the folded sidewall panels of triangular portions 60 which merge at their lower apices with the score lines 53, and at their upper ends with the small vertical panels 47, 48, 49 and 50. These small triangular portions 60 tend to brace the adjacent sidewalls against relative angular movement, resulting in a very rigid and easily handled carton structure. In this connection, it should also be noted that the left edge of the vertical wall panel 5 is so contoured as to conform, when folded into a tube, with the score lines 53, 52 and 59 on the glue flap 9, as well as with the edges of the short vertical panels 5i and 57. As will be seen in FIG. 13 showing a completed carton formed from the blank of FIG. 2, it will be apparent that this arrangement results in a very neat and attractive looking form of construction in the region of the glue flap, the junction of the panel 5 with the glue flap being hardly noticed. A similar construct-ion is also utilized in the blanks of FIGS. 1, 3 and 4.

A further modification is shown in FIG. 3, the carton blank having sidewall panels 5, '6, 7 and 8 and glue fiap panel 9 as was the case in the blanks already described. This end of the carton is provided wtih end flaps 16, 17, 18, 19 and extended glue flap 20*, separated respectively by cut lines 21, 22, 23 and 24, these lines terminating a short distance above a horizontal score line 15 defining the lower edges of the end flaps. In this case, the sidewall panels adjacent the central portion of the carton are arranged to hinge about vertical score lines 61, terminating at their upper ends at the junction of angularly disposed score lines 62, 63, 64, 65, 66, 67, 68, and 69. These latter score lines define fiat triangular panels 70, 71, 72 and 73, the upper ends of these panels being defined by the horizontal score line 15, and the vertical center lines of the panels being substantially in line respectively with the end flap cut lines 21, 22, 23 and 24. When the carton is folded to form a tube, the main side panels fold about the vertical score lines 61 to form a carton having a rectangular cross section in the central portion thereof, while the triangular panels converge inwardly from those score lines toward the horizontal score line 15, the material above the score line coverging slightly outwardly therefrom toward the lower ends of the cut lines between the end flaps. Here again, the corner construction when the end flaps are folded in overlapping relationship is substantially identical with that shown in FIG. 1, but the appearance of the finished carton is quite different from that of the carton of FIG. 1, and the carton is also much more rigid to handle. In this case, the left edge of the panel is contoured to conform, when the blank is folded in tubular shape, with the vertical score lines 61 and the score line 69 on the glue flap 9, see FIG. 14. It will be understood that the lower end of this carton blank may be formed in the same manner as the upper end as described, or that the lower end of the blank if desired may be formed as shown in FIGS. 2, 4 or 5.

A further modification is illustrated in FIG. 5, showing the upper portion of the carton blank. This blank includes main wall panels 5, 6, 7 and 8 and glue flap panel 9, these panels being connected by narrow fiat vertical corner panels 10, 11, 12 and 18 as already described in connection with FIG. 1. A horizontal score line 15 separates these wall panels from end flaps 74, 75, 76 and 77, and extended glue flap panel 78. These panels are separated respectively by cut lines 79, 80, '81 and 82, but it will be noted that these out lines are arranged differently from the cut lines shown in FIGS. 1, 2 and 3 insofar as they are related to the vertical center lines of the narrow vertical panels 10, 11, 12 and 13. By way of example, cut line 79 is positioned slightly to the left of and parallel with the vertical center line of the narrow vertical panel 19, and terminates at its lower end in a portion 83 curving downward to the right to the center line of the panel 10. In like manner, the vertical out line 80 is at the right of the vertical center line of the panel 11 and is curved downward to the left at its lower end at 84 toward the center line. The cut line 81 is disposed in the same manner as the cut line 79, and the out line 82 is disposed in the same manner as the cut line 80. Consequently, the panels 75 and 77 are wider than the corresponding panels 17 and 19 in FIG. 1, for example, and when folded inwardly at right angles to the adjacent sidewall panels 6 and 8, the upper corner portions of the end flaps 75, and 77 substantially conform to the outer peripheries of nibs 46b, and when adhesively secured together, serve to maintain the nibs in the plane of the carton ends. The folding of the flaps, however, takes places in substantially the same manner as in the other constructions heretofore described, the triangular portions at the corner above the horizontal score line 15 folding in a more or less bellows form and forming outwardly extending nibs as heretofore described, see FIGS. 9, and 11. It is to be understood in this connection, that the remaining portion of the carton may be constructed in the manner shown in FIGS. 1, 2, 3 or 4 if desired without departing from the spirit of the invention. In this case, it will be noted that the lower portion of the left side of the end flap 74 is formed at 85 with acontoured edge portion merging with the left edge of the panel 5, and adapted to conform to the curved portion formed on the right side of the upper ends of the blank by the curved portion at the lower end of the cut line 82.

It will also be noted that the left and right edges and the upper edges of the large flaps 75 and 77 are slightly curved in this embodiment of the invention. When the carton is in completed form, the sidewalls of the carton at the extreme ends are curved outward very slightly, and this contouring of the large end flaps is such that when the flaps are folded, their edges tend to conform more closely with the contour of the sidewall ends along the score line 15. In addition, due to the fact that the large end flaps are wider than those shown in the other embodiments, the left and right edges of these end flaps conform more fully with the upper ends of the narrow sidewall panels. Also, the large end flaps at their outer corners tend to cover the nibs 46b more fully, and being adhesively secured thereto, tend to maintain these nibs in a flatter condition than would otherwise be the case. The sift-proof corner construction is essentially the same,

cal

however, the paperboard in the small triangular portion above the score line 15 folding in substantially the same manner as heretofore described in connection with the other embodiments of the invention.

Upper portions of completed cartons formed from the blanks of FIGS. 1, 2 and 3 are shown in perspective in FIGS. l2l4, these views showing the junction of the opposite edges of the blank at the glue flap, and showing the outstanding nibs and the corner construction of the carton.

It will be apparent from the foregoing description that a novel carton construction has been provided, so constituted that the blanks are very economical in the use of paperboard, and have a substantially rectangular shape when completed, the blanks being of one-piece construction and requiring only a minimum amount of adhesive in order to secure the end flaps together in overlapping relationship. The unique corner construction, wherein, as shown in the drawings, fiat narrow corner panels are provided at the junction of the sidewalls and connected thereto along separate and distinct spaced apart score lines, and the outstanding nibs at the corners of the carton provide a carton having a very attractive appearance and great customer appeal, and the construction of the corners and the nibs at the corners is such that they can be repeatedly crushed or distorted in handling without detracting from the sift-proof feature of the carton. The carton can readily be formed into a tube on a mandrel or otherwise, and the end flaps then sealed either with the aid of pressure in a machine or by hand if so desired, it being particularly pointed out that the last end to be closed can be readily sealed in a sift-proof manner by pressure on the end of the carton, something which cannot be done with the conventional type of carton commonly used. In this connection, it is pointed out that the large flaps shown in FIG. 1, for example, need not be fully coated with adhesive, but that the adhesive may be applied as shown at the upper end of FIG. 2. This also applies to FIGS. 35. Here, a narrow band of adhesive 86 may be provided along the edge of the flap 17, and a similar band of adhesive '87 may be applied along the edge portion of the end flap 19, this being all that is necessary to insure a satisfactory sealing of the end of the carton. It will be understood, that adhesive will be applied along the left edge of the panel 5 and the left edges of the end flaps 16 and 29 in a manner similar to that shown in FIG. 1, in order to permit the panel 5 to be bonded to the outer surface of the glue flap 9, and to permit the end flaps 16 and 29 to be bonded effectively to the outer surfaces of the extended glue flap panels 20 and 33.

The construction is such that various types of adhesive may be utilized, and by way of example, the adhesive may be of the heat sealing variety printed on the flat blanks during manufacture, or a solvent type of adhesive can be printed on the blanks and activated by a suitable solvent during the sealing operation; If a heat-sealing type of adhesive is utilized, this can be activated by heat during the erection of the carton. This carton is also adapted to the use of so-called wet adhesive such as is commonly used in carton plants to side seam conventional carton blanks, it only being necessary that the adhesive have sufficient tack to hold the flaps together after they have been folded in overlapping relationship. This type of adhesive is normally lower in cost than so-called heat sealing and solvent types of adhesives and can be used very advantageously in the construction of cartons of this type.

The versatility of the carton construction described will be readily apparent to those skilled in the art, in view of the fact that the carton may be constructed in accordance with FIG. 1 to provide a package which has some of the characteristics of a bag in order to permit the user to readily dispense the contents, while some of the other forms described and illustrated provide for a particularly rigid carton while still retaining the advantages of the sift-proof corner. The carton forms shown entirely eliminate the necessity for an inner bag or an overwrap for the purpose of preventing sifting of the contents, and consequently this type of carton is much more economical than those which require an inner bag or an overwrap. No special techniques are required in forming the blank, and it is readily adaptable to production in carton plants already equipped for the manufacture of the more conventional type blanks.

The sealing of the ends can be accomplished entirely by hand if desired for small production runs, or the ends can be sealed by simple machinery which does not require great force to effect sealing of the end flaps. The sidewalls of the carton are rigid enough to permit the end flaps to be pressed downward to provide a fiat surface at the top end of the carton by exerting a downward pressure on the outer end flap by means of a suitable pressure plate which may be operated manually or in a suitable machine, not shown. Since it is only necessary to provide adhesion between the flaps along the outer edges thereof, it will be understood that the vertical sidewalls of the carton provide sufiicient rigidity to permit the flaps to be sealed together along these edges by suitable pressure on the top end of the closed carton. In the carton of ordinary construction wherein the corners of the carton comprise three adjacent walls at right angles to each other and meeting at a point, it is virtually impossible, after filling the carton, to close the upper end flaps and seal them in overlapping relationship without leaving pin holes at the corners through which the contents tend to escape. This difficulty is entirely overcome by the present invention. The carton also offers much better protection to the contents as compared with the ordinary carton, in view of the fact that there are no pin holes at the corners through which air or vapor can pass back and forth as the carton is subjected to various changes in temperature.

Although the cut lines separating the foldable end flaps have been illustrated as being single cut lines, it is to be understood that these end flaps may be separated by either single cut lines or by spaced apart cut lines without departing from the spirit of the invention. In addition to the above, it is also pointed out that the point of termination of these cut lines adjacent the horizontal score line 15 is not critical and that the lines if desired may terminate at the horizontal score line itself without detracting from the elficiency of the corner construction in preventing sifting of the carton contents. The arrangement shown, however, is the preferred form. It is also not essential to have the terminals of the cut lines located on the center line of the narrow panels which connected the main sidewall panels, as such terminals can be at either side of the center line provided they are positioned between extensions of the score lines which define the sides of the narrow vertical corner connecting panels. The important thing is to have a portion of each end flap at each side thereof integral with a portion of the narrow corner panels, thus providing the material necessary to provide the bellows type fold at the corner which produces the outstanding nib 461) when the carton flaps are folded. For convenience, the carton has been illustrated as having a generally rectangular cross-sectional form, but the invention is also applicable to other polygonal cartons having more or less than four main sidewall panels. It is also pointed out, that although the nibs 46b are preferably pressed down substantially into the plane of the outer end flap on the carton, this is not essential to the sift-proofness of the carton, and is done primarily for the sake of better appearance. The constructions shown in FIG. 2 to FIG. 5 can be used interchangeably on opposite ends or at different corners of a single carton if desired in order to provide a distinctive appearance to the carton for identification purposes or otherwise.

While several modifications of the invention have been illustrated and described herein with considerable particularity, it will be understood by those skilled in the art, that various changes and modifications may be made without departing from the spirit of the invention. Reference will, therefore, be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. A flat blank for a tubular sift-proof carton of generally rectangular cross section, said blank including four flat main vertical sidewall panels, and a vertical glue flap panel at one side of the blank, the adjacent sidewall panels and the outer sidewall panel and glue flap panel at said one side of the blank being connected, at least at the upper end portion of the blank, by flat narrow vertical corner panels along separate spaced apart vertical score lines, foldable end flaps at the upper ends of said sidewall panels and glue flap panel connected thereto along a common horizontal score line, out lines separating the adjacent foldable end flaps, each cut line terminating at a point adjacent to but spaced above said horizontal score line, each of said cut lines being substantially in alignment with the vertical center line of the corresponding flat corner panel, the inner end of each out line and the ends of the horizontal score line at the upper end of said corresponding fiat corner panel forming the apices of a small flat triangular panel, each said small triangular panel being integral with a pair of ad jacent foldable end flaps and with the adjacent flat corner panel, and the other side of said blank, at least at said upper portion thereof, having a vertical. edge on the other outer sidewall panel, adapted when the blank is folded to form a tube having the adjacent sidewall panels at right angles to each other, to register with the score line between the glue flap panel and the adjacent corner panel, and to terminate at the junction of said last named score line and said common score line, an edge on the end flap at the end of said other outer sidewall panel extending angularly outward and upward from said junction and having a length and being at an angle to said common horizontal score line such that the lower end of said angularly extending edge is substantially in register with the junction of said common horizontal score line and the upper end of the score line between the glue flap and adjacent flat corner panel and the other end of said angularly disposed edge is substantially in register with the lower end of the out line separating the foldable end flaps at the upper ends of the glue flap panel and the adjacent sidewall panel, and a vertical edge on the side of the end flap at the upper end of said other sidewall panel extending upward from the upper end of said angularly disposed edge and adapted to register through at least a portion of its length with the edge of the foldable flap at the upper end of said glue flap formed by the out line between said last named flap and the adjacent foldable end flap.

2. A sift proof corner construction for a tubular fiber board carton of generally rectangular cross section, said corner construction including a pair of main sidewall panels disposed at right angles to each other, a flat narrow corner panel integral with said sidewall panels and connected thereto along separate spaced apart score lines, the included angle in the interior of the carton between each sidewall panel and said flat narrow corner panel being a common score line extending across the ends of the sidewall panels and flat corner panel at the end of the carton, a small triangular panel at the end of said fiat corner panel integral therewith and having its base along said score line and folded outwardly of the corner panel with its apex positioned outwardly of the plane of the corner panel, foldable end flaps at the ends of said sidewall panels separated by a cut line and folded in overlapping relationship about said common score line and adhesively secured together, said cut line, when said end flaps are so folded, terminating at said apex of said small triangular panel, a corner portion of one end flap adjacent the end of said out line and said common score line being folded over said small triangular panel and a corner portion of the other of said end flaps adjacent the end of said out line and adjacent said common score line being folded over said first named end flap corner portion, said small triangular panel and said end flap corner portions forming a triangular nib on the outside of the carton having its apex positioned outside the plane of said fiat narrow corner panel.

941,356 Byrne Nov. 30, 1909 Jenkins Dec. 28, Weiss July 13, 'Gruenberg Dec. 5, Paige Aug. 11, Eaton May 13, Benschoter Sept. 4, Sharts Mar. 5, Guyer Apr. 15,

FGREIGN PATENTS France Feb. 11, 

